1. Field of the Invention
The present invention relates to an optical recording medium, and more particularly, to an optical recording medium and a method for fabricating the same, which enable overwriting at high density.
2. Background of the Related Art
Generally, an optical recording method records and reproduces information in a non-contact mode. Therefore, problems regarding head crash that may occur in a magnetic recording method can be solved fundamentally. Also, as compared with the magnetic recording medium, the optical recording medium has advantages that it permits a disk to be exchanged with another one, it is portable, and it has a small track pitch, so that higher recording density can be achieved. In this respect, the optical recording medium has received much attention, and research and development on the optical recording medium have been progressed.
The optical disk technology trends to high density and high speed and thus more strict jitter margin is required.
An optical disk which is commercially used has four- to five-layered structure grown on a transparent polycarbonate substrate.
In case of a phase-change optical disk, overwriting is possible. Such a phase-change optical disk will be described with reference to FIG. 1. As shown in FIG. 1, the optical disk is fabricated in such a manner that a lower dielectric layer, an information recording layer, an upper dielectric layer, and a reflecting layer are sequentially formed on a substrate by sputtering process under high vacuum state, and a passivation layer is formed by spin-coating a UV curing resin. At this time, one more layer may additionally be formed to improve recording cyclicity.
However, the related art optical disk has several problems.
For a phase-change optical disk, the jitter value of a recorded signal during the initial stage of a direct overwrite(DOW) cycle is usually much larger than that during the initial writing. Data reading error can occur while the disk is running in the drive when the jitter of the media is over a critical limit. The origin of a jitter bump is closely related to the crystallization rate, which is initially not sufficiently fast to match the linear velocity of the disk. That is, in the case of 2 DOW cycles, some marks have an amorphous tail in the tailing edge, which induces increase of the jitter value. The mark which has a tail is in the crystalline matrix which has large grains, while the mark which has a sharp trailing edge is located in the crystalline matrix which has small grains. Jitter was reduced after 100 DOW cycles. In the case of 100 DOW cycles, the mark has a sharp tailing edge without a tail and the crystalline matrix is composed of large grains.
The origin of jitter increase during the initial DOW cycle is mark-tail remaining. Previous marks did not crystallize completely at the level of erasing laser power. The previous mark of the center zone in the track width remained as a tail, while that of the side zone was crystallized as large grains by the grain growth process. This phenomenon occurs because the crystallization rate is initially not sufficiently fast to match the linear velocity of the disk.
Therefore, a problem of the jitter bump should be solved.
Accordingly, the present invention is directed to an optical recording medium and a method for fabricating the same, that substantially obviate one or more of the problems due to limitations and disadvantages of the related art.
An object of the present invention is to provide an optical recording medium and a method for fabricating the same, in which a jitter bump, which is increased during an initial DOW cycle, is reduced.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described, an optical recording medium including at least one dielectric layer, at least one recording layer, and a reflecting layer on a substrate, is characterized in that an interface layer is formed on either at least one of lower and upper surfaces of the recording layer or one surface of the lower and upper surfaces of the dielectric layer, adjacent to the recording layer, at a predetermined thickness, wherein the interface layer is formed by reacting any one of the recording layer and the dielectric layer with any one of N, O and C ions.
In one preferred embodiment of the present invention, the interface layer formed on the recording layer has a thickness of 5 nm or below and the interface layer formed on the dielectric layer has a thickness of 10 nm or below. Further, the recording layer is composed of any one material selected among a GeSbxe2x80x94Sb2Te3 based material, a material in which one of Ag, Se, In and Co is added to the GeSbxe2x80x94Sb2Te3 based material at about 10 at % (atomic percent) or below, and an Agxe2x80x94Inxe2x80x94Sbxe2x80x94Te based material, while the dielectric layer is composed of any one material selected among ZnSxe2x80x94SiO2, SiO2, (ZrxCe1xe2x88x92x)O1xe2x88x92y, AlN, and Al2O3.
In another aspect, a method for fabricating an optical recording medium including at least one dielectric layer, at least one recording layer, and a reflecting layer on a substrate, the method comprising the steps of: implanting any one of N, O and C ions into the substrate when forming the recording layer or the dielectric layer to react with any one of the recording layer or the dielectric layer; and forming an interface layer on the recording layer or the dielectric layer.
In another embodiment of the present invention, the recording layer is composed of any one material selected among a GeSbxe2x80x94Sb2Te3 based material, a material in which one of Ag, Se, In and Co is added to the GeSbxe2x80x94Sb2Te3 based material at about 10 at % (atomic percent) or below, and an Agxe2x80x94Inxe2x80x94Sbxe2x80x94Te based material. The dielectric layer is composed of any one material selected among ZnSxe2x80x94SiQ2, SiO2, (ZrxCe1xe2x88x92x)O1xe2x88x92y, AlN, and Al2O3. Further, the interface layer is formed by reactive sputtering.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.